The present invention relates to an improved version of a caltrop. The American Heritage Dictionary of the English Language, 3rd ed., 81992, Houghton Mifflin Co., herein incorporated by reference, defines a caltrop as: a metal device with four projecting spikes so arranged that when three of the spikes are on the ground, the fourth points upward, used as a hazard to pneumatic tires or to the hooves of horses.
Although the basic form and function of a caltrop are well known, modern improvements in such areas as tire composition and puncture resistance along with increased vehicle weights and required penetration forces necessitate improvements to the known prior art. In addition, specific requirements by military or law enforcement may further compel improvements or specialization of tire puncture devices.
For example, one prior art caltrop having two cylindrical metal bars bent and welded together to form four cylindrical metal spikes may puncture a tire and remain in it thereafter so that the spike actually plugs the hole and prevents deflation. Or, the tire may actually reseal the puncture thereby preventing deflation.
Prior attempts have been made to try to improve caltrop design but are not as effective or versatile as the current invention. For example, although other prior art caltrops, such as one designed by a National Laboratory made of two planar pieces of sheet metal joined along a seam formed by the axis of two of the spikes, may be better than the round spike type at preventing resealing of the puncture, it may become wedged in the tire and prevent rapid deflation. Additionally, empirical data show that in certain orientations, the tips of this type of caltrop bend over or the entire caltrop tends to fold like a "taco" rather than puncturing the tire.
The present invention was designed in response to military need for an effective, versatile, dependable, and cost effective tire deflation device. The design of the present invention is a significant improvement over the prior art in several respects. It has proven to be more reliable, effective, and versatile. In addition, the present invention can be manufactured cost effectively.